Project summary: Phonation is a component of speech communication, with a highly complex interplay of physiological and physical properties. Phonation is the vibratory system in the larynx that converts air flow from the lungs into sound in the throat. This process of vocal fold vibration and the conversion of air flow into sound is insufficiently understood for the purposes of making precise diagnostic decisions in the voice clinic, targeting optimal intervention strategies for voice problems, and achieving high quality articulatory speech synthesis. The long range goal of this research program is to develop efficient and highly effective computer models of phonation that take into account the motion of the vocal folds and and dynamic flow-acoustic interactions for both normal and pathological laryngeal conditions. This continuation proposal focuses on the details of the basic physics dealing with the conversion of airflow to sound and the air pressures contributing to vocal fold oscillation through the use of various physical and computational models. The aims are to 1) determine the basic aerodynamic causes of vocal fold oscillation, 2) determine the basic flow structure and sound sources (aeroacoustics) related to phonation, 3) create valid and complementary simulation models of phonation, 4) model the phonatory effects of asymmetric conditions (oblique glottis, tissue asymmetries, pathologies), and 5) determine the role of surface hydration and humidity on phonation. This research program is a collaboration among the Bowling Green State University, Purdue University, and the University of Toledo, with participation from consultants at the University of Cincinnati and ATR Human Information Science Laboratories in Kyoto, Japan. Relevance to public health: The basic studies and developing models of this research program are intended to broaden health professionals' knowledge of phonatory mechanics, and develop modeling tools that will aid the clinical and surgical treatment of voice disorders.